New tournament, old rivalry: Novak Djokovic beats Rafael Nadal to send ATP Cup final to decisive doubles showdown (VIDEO)

Going into the match, the 16-time Grand Slam winner knew he could not afford to lose, as Serbia were trailing 1-0 after Roberto Bautista Agut outplayed Dusan Lajovic 7-5, 6-1 to give Spain an early ATP Cup final lead.

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A win for Nadal over Djokovic would have meant an overall victory for Spain. However, the reigning Australian Open champion had no plans to lose, prolonging the gold-medal tie into a decisive doubles match.

Djokovic got off to an excellent start, making the double break to take a more-than-confident 5-2 lead which he never squandered, winning the first set 6-2.

Nadal tried to reverse the course of the game, but his efforts were not enough to beat his well-known Serbian counterpart, who was more focused during the tie-break and took the second set 7-6.

With that triumph, Djokovic has celebrated his ninth consecutive hard-court victory against the Spaniard.

The decisive doubles match between Spain and Serbia will be played later on Sunday.